Coastal was selected to perform the abandoned mine void grouting as part of the construction of a retail store located near Centerville, Iowa. Due to the abandoned mine being flooded, the project required strict erosion and sediment controls to deal with drill and grout spoils as well as mine water encountered during the work.
The objective of the Mine Grouting Program is to stabilize abandoned mine workings located below the building pad. As a Subcontractor to the General Contractor for the project, Coastal’s portion of the work included drilling strategically located boreholes, placing of PVC and injection of three site specific grout mixes.
The area beneath the parcel in which the retail facility was to be constructed had been previously mined. In order to build on the desired location, mine grouting was necessitated. This grouting enhanced the underlying structural soundness of the site and therefore allowed an otherwise unsuitable parcel to be utilized.
LF of drilling
Site-specific group mixes developed
CY of grout injected
The mine workings were stabilized by injecting a low strength grout mixture into the void and rubble zones. The grout material also filled voids and seams in the rock overburden that resulted from prior subsidence.
The scope of the mine grouting work included the construction of a barrier in the mine void and then grouting of the interior area of the stabilization limits. The injection of interior grout began on a 64’x64’ grid with holes split spaced resulting in a 32’ grid following barrier construction. Grout takes and mine conditions were constantly monitored and a suite of grout mixes including a high flow grout, a medium flow grout and a high slump grout were developed. Grout was mixed onsite in a volumetric plant and pumped directly to the injection holes. After the barrier was grouted, the interior holes were pumped to refusal to completely fill the flooded mine.
